Synthesis and antioxidant activity of thymol and carvacrol based Schiff bases

Antioxidant activity of Schiff base ligands using the DPPH scavenging assay: an updated review

Schiff base ligands, formed from primary amines and carbonyl compounds, are potential antioxidants because they scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals via hydrogen atom transfer (HAT) and single electron transfer (SET) routes. This review aims to help design, synthesize, and discuss the antioxidant activity of Schiff base ligands based on their structure. This study critically discussed the solvent effect and the structural changes of Schiff base ligands responsible for DPPH scavenging activity, such as proton donating, electron-donating, and electron-withdrawing substituents, conjugation and ring structure. The ligands with electron-donating substituent groups in the phenolic ring demonstrated greater activity by readily stabilizing the radical and some of them showed higher activity than the standard. The activity also depends on the solvent used; the activity increases in those solvents that promote the proton and electron donation of the Schiff base. Schiff bases are most important due to their versatile applications, which can be explained by their antioxidant activity. The data led to the conclusion that the Schiff base ligand will serve as a source of synthetic antioxidants. There should be lots of scope for research on the antioxidant activity of Schiff bases. This review will assist researchers in studying Schiff base-based antioxidants and their applications. All the data analyzed in this paper was found from in vitro tests; for more clearance supplementary tests and in vivo investigations are crucial.

Extension of shelf life of tomato (Solanum lycopersicum L.) by using a coating of polyhydroxybutyrate-carboxymethyl cellulose-pectin-thymol conjugate

This study targets explicitly finding an alternative to petroleum-based plastic films that burden the environment, which is a high priority. Hence, polymeric films were prepared with carboxymethyl cellulose (CMC) (4%), pectin (2%), and polyhydroxybutyrate (PHB) (0.5%) with different concentrations of thymol (0.3%, 0.9%, 1.8%, 3%, and 5%) and glycerol as a plasticizer by solution casting technique. The prepared films were tested for mechanical, optical, antimicrobial, and antioxidant properties. Film F5 (CMC + P + PHB + 0.9%thymol) showed an excellent tensile strength of 15 MPa, Young's modulus of 395 MPa, antioxidant activity (AA) (92%), rapid soil biodegradation (21 days), and strong antimicrobial activity against bacterial and fungal cultures such as Klebsiella pneumoniae, Staphylococcus aureus, Escherichia coli, Aspergillus niger, and Aspergillus flavus. The thymol content increase in films F6 (1.8%), F7 (3%), and F8 (5%) displayed a decrease in mechanical properties due to thymol's hydrophobicity. For shelf life studies on tomatoes, F2, a film without thymol (poor antimicrobial and antioxidant activities), F5 (film with superior mechanical, optical, antimicrobial, and antioxidant properties), and F7 (film with low mechanical properties) were selected. Film F5 coatings on tomato fruit enhanced the shelf life of up to 15 days by preventing weight loss, preserving firmness, and delaying changes in biochemical constituents like lycopene, phenols, and AA. Based on the mechanical, optical, antimicrobial, antioxidant, and shelf life results, the film F5 is suitable for active food packaging and preservation. PRACTICAL APPLICATION: The developed active biodegradable composite can be utilized as a coating to extend the shelf life of fruits and vegetables. These coatings are easy to produce and apply, offering a sustainable solution to reduce food waste. On an industrial scale, they can be applied to food products, ensuring longer freshness without any technical challenges.

Synthesis and evaluation of in vitro antioxidant, anticancer, and antibacterial properties of new benzylideneiminophenylthiazole analogues

A series of new benzylideneiminophenylthiazole analogues were designed and synthesized. Common spectroscopic methods, such as FT-IR, 1H-, 13C-NMR, and MASS spectra, and elemental analysis, were used to confirm the molecular structures. Then, the antioxidant, cytotoxicity, and anti-bacterial effects of synthesized analogues were assessed against 2,2-diphenyl-1-picrylhydrazyl (DPPH), three cancer cell lines, and two bacterial strains, respectively. Among the analogues, 7f was detected as the most potent compound for antioxidant activity. Moreover, the compounds 7b, 7f, and 7 g exhibited the maximum cytotoxicity activity against MCF-7, HepG-2, and A549 cell lines, respectively. Finally, 7e showed the highest anti-bacterial activity against both S. aureus and E. coli strains. It was concluded from the antioxidant, cytotoxicity, and anti-bacterial effects that the benzylideneiminophenylthiazoles might serve as candidate molecules for the development of small molecules with medicinal potential.

Polyphenols in edible plant leaves: an overview of their occurrence and health properties

Edible plant leaves (EPLs) constitute a major renewable functional plant biomass available all year round, providing an essential source of polyphenols in the global diet. Polyphenols form a large family of antioxidant molecules. They protect against the harmful effects of free radicals, strengthen immunity and stimulate the body's natural defenses thanks to their antibacterial and antiviral functions. This study refers to phenolic compounds from 50 edible plant leaves divided into four categories: green leafy vegetables, underutilized leafy vegetables, leafy spices and leafy drinks. It provides data on the identification, occurrence and pharmacological functions of polyphenols contained in EPLs, and provides a better understanding of trends and gaps in their consumption and study. Certain EPLs, such as moringa (Moringa oleifera Lam.), tea (Camellia sinensis L.) and several leafy spices of the Lamiaceae family, reveal important characteristics and therapeutic potential. The polyphenol composition of EPLs makes them functional plants that offer relevant solutions in the fight against obesity, the management of food insecurity and the prevention of chronic diseases.

Design, spectroscopic characterization, in silico and in vitro cytotoxic activity assessment of newly synthesized thymol Schiff base derivatives

Cancer is a global public health problem affecting millions of people every year. New anticancer drug candidates are needed to overcome the resistance to drugs used in the treatment of various types of cancer. In this study, two new series of benzenesulfonate-based thymol derivatives (14-19 and 20-25) were synthesized for the first time as promising chemotherapeutic agents and characterized using FT-IR, 1D NMR (1H- and 13C-NMR, APT, DEPT 135), 2D NMR (HETCOR and HMBC), and elemental analysis (CHNS). Antiproliferative activity of the molecules was determined against cancer cell lines, namely, the human lung adenocarcinoma cell line (A549) and the colorectal adenocarcinoma cell line (DLD-1), using MTT method for both 48 and 72 h. Compounds (14-25) showed cytotoxic activities against A549 with IC50 values ranging from 9.98 to 81.83 μM, respectively, compared to cisplatin (6.65 μM). These compounds exhibited antiproliferative activities against DLD-1 cancer cells at concentrations ranging from 4.29 to 53.62 μM, respectively, compared to cisplatin (9.91 μM). Especially, compound 16 displayed significant cytotoxicity on A549 and DLD-1 cancer cells with IC50 values of 9.98 and 10.75 μM, respectively. Finally, molecular docking studies were performed with Bcl-2, VEGFR-2, EGFR, and HER2 targets using the Schrödinger 2021-2 Maestro Glide program. The binding energy values and binding interactions of compounds 16 and 22 were determined to be the result of their interactions with these targets. Schrödinger 2021-2 Qikprop wizard drug similarity ratios and ADME prediction of all compounds 14-25 were also calculated.Communicated by Ramaswamy H. Sarma.

Biological evaluations and computational studies of newly synthesized thymol-based Schiff bases as anticancer, antimicrobial and antioxidant agents

Three new thymol-based molecules were synthesized and evaluated as anticancer, antimicrobial and antioxidant agents. Liver, colon, lung and prostate cancer cell lines were utilized in cytotoxicity tests. The results demonstrated that synthesized molecules had a cytotoxic effect against the screened cell lines. One of the molecules (4a) was found to have a higher efficacy towards the colon cancer cell line (DLD-1) with an IC50 value of 12.39 µM and the other (4c) towards the prostate cancer cell line (PC3) with an IC50 value of 7.67 µM than the positive control drug cisplatin. To assess the antimicrobial activity of molecules (4a-c), Gram-positive bacteria, Gram-negative bacteria and yeast were subjected to agar disc diffusion and broth microdilution assays. The investigation of antioxidant potential was conducted using the DPPH radical scavenging activity assay. While all compounds displayed strong cytotoxic and antioxidant properties, they exhibited only moderate antimicrobial activity. Molecular docking studies were performed on epidermal growth factor receptor (EGFR), vascular endothelial growth factor receptor 2 (VEGFR-2), focal adhesion kinase (FAK), B-Raf and phosphoinositide 3-kinase (PI3K). The binding energies and interactions obtained from the docking results of compounds (4a-c) supported the experimental results. Drug similarity rates and pharmacokinetic properties were analyzed with the absorption, distribution, metabolism and excretion (ADME) method. Geometric parameters such as chemical potential (µ), electrophilicity index (ω) and chemical softness (σ) of compounds (4a-c) were calculated using the 6-31*G basis set B3LYP method.Communicated by Ramaswamy H. Sarma.

Assessing the Antioxidant Benefits of Topical Carvacrol and Magnolol Periodontal Hydrogel Therapy in Periodontitis Associated with Diabetes in Wistar Rats

It is well recognized that oxidative stress contributes to chronic stress-induced cytotoxicity, which is a major factor in the progression of many diseases, including periodontitis and diabetes. Formulas based on natural extracts with antioxidant properties are alternative treatment perspectives in the management of such diseases. The aim of our study was to assess how carvacrol and magnolol influence periodontitis associated with diabetes in Wistar rats. Ninety Wistar rats were distributed in nine groups: I-control group; II-diabetes group (D); III-periodontitis group (P); IV-periodontitis and diabetes group (PD); V-periodontitis and diabetes with vehicle alone (PDV); VI-periodontitis and diabetes treated with carvacrol (PDC); VII-periodontitis and diabetes treated with magnolol (PDM); VIII-periodontitis and diabetes treated with carvacrol and magnolol (PDCM); IX-healthy group with vehicle alone (CV). Blood malondialdehyde (MDA) levels and catalase activity levels (CAT) were measured as indicators of oxidative stress and antioxidant capacity, respectively. Where diabetes and periodontitis were induced, MDA was augmented and CAT was depleted significantly. Whether given alone (PDM) or in combination with carvacrol (PDCM), magnolol significantly decreased MDA. Between the PDM group and the PDCM group, there were no notable differences. In Wistar rats with periodontitis related to diabetes, topical use of hydrogels containing magnolol, either alone or in combination with carvacrol, may reduce oxidative stress.

Friedelin and Glutinol induce neuroprotection against ethanol induced neurotoxicity in pup's brain through reduction of TNF-α, NF-kB, caspase-3 and PARP-1

Ethanol administration triggers an inflammatory response that leads to a complex series of immune responses including the release of an excessive amount of inflammatory mediators particularly tumor necrosis factor (TNF-α) and nuclear factor-kB (NF-KB) which produce a large amount of reactive oxygen species. The inflammatory-induced cytotoxicity is increased when the PI3-kinase/Akt pathway is inhibited. Some studies have also shown that ethanol suppresses the PI3-kinase signaling pathway induced by receptor activation. Friedelin and Glutinol belong to pentacyclic triterpenoid class and are known for their anti-inflammatory and antioxidant properties. The present study was aimed to elucidate the effects of these phytoconstituents on one of the key ethanol-induced neuronal damage pathways. The pups having (5-7 g average body weight) were used and randomly divided into groups. The control and ethanol treated pups were administered 0.9% normal saline while treated pups received glutinol and friedelin (30 mg/kg subcutaneously) respectively. After four hours all the experimental animals were sacrificed and their brains were collected carefully for protein expression analysis of p-Akt, TNF-α, NF-KB, caspase-3 and PARP-1 employing immunoblotting technique. Hemolytic, DNA protection, chelating power and β-carotene assays results revealed that freidelin and glutinol are safe for parenteral administration. Glutinol administration with ethanol significantly abridged the ethanol induced over expression of TNF-α, caspase-3 and PARP-1 in pup's brain. Similarly, freidelin attenuated the neurodegeneration by inhibiting the ethanol induced p-JNK and NF-kB expression in pups' brain. This protection may be attributed to the revival of p-Akt signaling for cell survival. It is concluded that the present study demonstrates the neuro-protective effects of friedelin and glutinol via modulating the capase-3 and PARP-1 expression and modulating the neuronal apoptotic pathways.

Graphene Oxide/Cholesterol-Substituted Zinc Phthalocyanine Composites with Enhanced Photodynamic Therapy Properties

In the present work, cholesterol (Chol)-substituted zinc phthalocyanine (Chol-ZnPc) and its composite with graphene oxide (GO) were prepared for photodynamic therapy (PDT) applications. Briefly, Chol-substituted phthalonitrile (Chol-phthalonitrile) was synthesized first through the substitution of Chol to the phthalonitrile group over the oxygen bridge. Then, Chol-ZnPc was synthesized by a tetramerization reaction of Chol-phthalonitrile with ZnCl2 in a basic medium. Following this, GO was introduced to Chol-ZnPc, and the successful preparation of the samples was verified through FT-IR, UV-Vis, 1H-NMR, MALDI-TOF MS, SEM, and elemental analysis. Regarding PDT properties, we report that Chol-ZnPc exhibited a singlet oxygen quantum yield (Φ∆) of 0.54, which is slightly lower than unsubstituted ZnPc. Upon introduction of GO, the GO/Chol-ZnPc composite exhibited a higher Φ∆, about 0.78, than that of unsubstituted ZnPc. Moreover, this enhancement was realized with a simultaneous improvement in fluorescence quantum yield (ΦF) to 0.36. In addition, DPPH results suggest low antioxidant activity in the composite despite the presence of GO. Overall, GO/Chol-ZnPc might provide combined benefits for PDT, particularly in terms of image guidance and singlet oxygen generation.

Antioxidant, Antibacterial and Antibiofilm Activity of Nanoemulsion-Based Natural Compound Delivery Systems Compared with Non-Nanoemulsified Versions

This study aimed to develop nanoemulsions with a focus on improving the bioactivity of oregano essential oil (OEO), carvacrol and thymol for possible food applications. Nanoemulsions were prepared with acoustic cavitation using ultrasound. The nanodroplets had average diameters of 54.47, 81.66 and 84.07 nm for OEO, thymol and carvacrol, respectively. The main compound in OEO was carvacrol (74%), and the concentration in the nanoemulsions was 9.46 mg/mL for OEO and the isolated compounds. The effects of droplet size reduction on antioxidant, antibacterial and antibiofilm activity were evaluated. Regarding antioxidant activity, the nanoemulsions performed better at the same concentration, with inhibitions >45% of the DPPH radical and significant differences compared with their non-nanoemulsified versions (p < 0.05). The nanoemulsions' minimum inhibitory concentration (MIC) and non-nanoemulsified compounds were evaluated against foodborne pathogens with inhibition ranges between 0.147 and 2.36 mg/mL. All evaluated pathogens were more sensitive to nanoemulsions, with reductions of up to four times in MIC compared with non-nanoemulsified versions. E. coli and S. Enteritidis were the most sensitive bacteria to the carvacrol nanoemulsion with MICs of 0.147 mg/mL. Concerning antibiofilm activity, nanoemulsions at concentrations up to four times lower than non-nanoemulsified versions showed inhibition of bacterial adhesion >67.2% and removal of adhered cells >57.7%. Overall, the observed effects indicate that droplet size reduction improved the bioactivity of OEO, carvacrol and thymol, suggesting that nanoemulsion-based delivery systems for natural compounds may be alternatives for food applications compared with free natural compounds.

Chemical composition, antioxidant and anti-inflammatory properties of Monarda didyma L. essential oil

In the present study, Monarda didyma L. essential oil (isolated from the flowering aerial parts of the plant) was examined to characterize its chemotype and to evaluate, in addition to the quali-quantitative chemical analysis, the associated antioxidant and anti-inflammatory activities. The plants were grown in central Italy, Urbino (PU), Marche region. Different analyses (TLC, GC-FID, GC-MS and ¹H-NMR) allowed the identification of twenty compounds among which carvacrol, p-cymene and thymol were the most abundant. On this basis, the chemotype examined in the present study was indicated as Monarda didyma ct. carvacrol. The antioxidant effect was assessed by DPPH assay. Moreover, this chemotype was investigated for the anti-inflammatory effect in an in vitro setting (i.e., LPS-stimulated U937 cells). The decreased expression of pro-inflammatory cytokine IL-6 and the increased expression of miR-146a are suggestive of the involvement of the Toll-like receptor-4 signaling pathway. Although further studies are needed to better investigate the action mechanism/s underlying the results observed in the experimental setting, our findings show that M. didyma essential oil is rich in bioactive compounds (mainly aromatic monoterpenes and phenolic monoterpenes) which are most likely responsible for its beneficial effect.

Chemical and Biological Activity Profiling of Hedyosmum strigosum Todzia Essential Oil, an Aromatic Native Shrub from Southern Ecuador

The present study aimed to determine the chemical composition, enantiomeric distribution and the biological profile of Hedyosmum strigosum essential oil (EO). The antioxidant properties and anticholinesterase effect were measured by spectroscopic methods and antimicrobial potency assessed against 8 bacteria and two fungi. H. strigosum is a native shrub, particularly found in Ecuador and Colombia at 2000 to 3500 m a.s.l. Chemical composition was determined by GC-MS and GC-FID. A total of 44 compounds were detected, representing more than 92% of the EO composition. The main compounds were thymol (24.35, 22.48%), α-phellandrene (12.15, 13.93%), thymol acetate (6.59, 9.39%) and linalool (8.73, 5.82%), accounting for more than 51% of the EO. The enantioselective analysis revealed the presence of 5 pure enantiomers and 3 more as a racemic mixture. The EO exerted a strong antioxidant capacity, determined by ABTS assay, with a SC50 of 25.53 µg/mL and a strong and specific antimicrobial effect against Campylobacter jejuni with a MIC value of 125 µg/mL. A moderate acetylcholinesterase inhibitory effect was also observed with an IC50 value of 137.6 µg/mL. To the best of our knowledge this is the first report of the chemical composition and biological profile of H. strigosum EO.

The Effect of Thymus vulgaris L. Hydrolate Solutions on the Seed Germination, Seedling Length, and Oxidative Stress of Some Cultivated and Weed Species

The aim of this study was to determine the effect of the hydrolates obtained as the by-products of the Thymus vulgaris essential oil steam distillation process. The bioassays, which were undertaken in order to determine the effect on germination and initial growth of seedlings of some cultivated and weed species, were performed under controlled conditions with different concentrations of the hydrolates. Seeds of Glycine max, Helianthus annuus, Zea mays, Triticum aestivum, Daucus carota subsp. sativus, Allium cepa, Medicago sativa, and Trifolium repens, and six weed species—Amaranthus retroflexus, Chenopodium album, Portulaca oleracea, Echinochloa crus-galli, Sorghum halepense, and Solanum nigrum—were treated with 10, 20, 50, and 100% T. vulgaris hydrolate solution. The obtained results showed that the T. vulgaris hydrolate had the least negative effect on the germination of cultivated species, such as soybean, sunflower and maize, whereas clover and alfalfa were the most sensitive. By comparison, all the tested weed species expressed high susceptibility. It can be concluded that the T. vulgaris hydrolate has an herbicidal effect, in addition to its potential as a biopesticide in terms of integrated weed management.

Synthesis, spectral studies, antioxidant and antibacterial evaluation of aromatic nitro and halogenated tetradentate Schiff bases

Herein, we report the synthesis, characterization, and biological properties of eleven (3a-3k) novel Schiff bases. The spectral data of FT-IR, ¹H NMR, ¹³C NMR, and LC-MS are associated with these synthesized compounds. From the FT-IR analysis, we confirmed the azomethine (-C=N-) group and from ¹H NMR data, the phenolic –OH proton is appeared at range δ 13.92–14.09ppm due to hydrogen bonding. The LC-MS analysis agreed with molecular ion peaks of synthesized Schiff bases. To evaluate the antibacterial activity of newly synthesized compounds were screened against b. licheniformis, b. species, e. coli, and s. aureus. Furthermore, the antioxidant activity was investigated by two methods 2,2-diphenyl-1-picryl hydrazyl (DPPH) and hydroxyl radical scavenging methods. The (-NO₂,-Cl,-Br,-I) substituted compounds have shown good antibacterial activity against tested organisms. Also, these compounds were exhibited higher antioxidant activity by given methods.

Phytochemical Variability of Essential Oils of Two Balkan Endemic Species: Satureja pilosa Velen. and S. kitaibelii Wierzb. ex Heuff. (Lamiaceae)

Satureja pilosa and S. kitaibelii (Lamiaceae) are Balkan endemic plant species, and the composition of their essential oil (EO) is highly variable. The aim of the present study was to establish: (1) the EO variability in two populations of S. pilosa (the intrapopulation), and (2) the EO variation in S. kitaibelii between nine populations (interpopulation) from Bulgaria and two from Serbia. The EOs of two Satureja species were obtained from aboveground plant parts by hydrodistillation and were analyzed by GC/MS/FID. Overall, the EO yield on the intrapopulation level of S. pilosa varied from 0.54% to 2.15%, while the EO of S. kitaibelii varied from 0.04% to 0.43% (interpopulation). The EO of S. pilosa was found to contain thymol and carvacrol as the main constituents, with other major constituents being p-cymene and γ-terpinene. S. pilosa samples in both studied populations formed six chemical groups. The major constituents (p-cymene, terpinen-4-ol, bornyl acetate, γ-muurolene, endo-borneol, cis-β-ocimene, trans-β-ocimene, carvacrol, α-pinene, thymoquinone, geranial, geranyl acetate, spathulenol, and caryophyllene oxide) of S. kitaibelii EO were considered for grouping the populations into ten chemotypes. The present study is the first report on the interpopulation diversity of S. kitaibelii EOs in Bulgaria. It demonstrated variability of the EOs between and within the populations of S. kitaibelii from Bulgaria. This study identified promising genetic material that could be further propagated and developed into cultivars for commercial production of S. kitaibelii and S. pilosa, thereby reducing the impact of collection on wild populations.

Antioxidant capacity of phenolic compounds separated from tea seed oil in vitro and in vivo

Tea seed oil is rich in phenols with good antioxidant capacity. However, the antioxidant capacity evaluation of tea seed oil polyphenols is not deep enough, which mainly focusing on the evaluation of the chemical system. Thirty-nine phenols were tentatively identified by UPLC-ESI-MS/MS analysis, including flavonoids and phenolic acids. The antioxidant capacity of phenol extracts was investigated in vitro and in vivo. The chemical assays showed the extracts had good proton and electron transfer capabilities. The CAA assay indicated the IC₅₀ of the extracts was 77.93 ± 4.80 µg/mL and cell antioxidant capacity of the extracts was 101.05 ± 6.70 μmol·QE/100 g of oil. The animal experiments suggested phenol extracts could significantly improve the organ index, reduce malondialdehyde content, and increase superoxide dismutase, glutathione peroxidase and total antioxidant capacity (p < 0.05). This study was contributed to the antioxidant capacity of phenol extracts of tea seed oil by comprehensive evaluation.

A critical analysis of research methods and experimental models to study tooth discolouration from endodontic materials

As a range of materials used in endodontics may cause tooth discolouration, exploration of factors responsible for the darkening of the tooth crown or root is warranted. This narrative review paper discusses the range of technical factors that apply in laboratory studies that assess endodontic discolouration. As an example of how these factors operate, particular examples relating to discolouration caused by endodontic medicaments containing tetracycline antibiotics are used. Following the PRILE 2021 guidelines approach, a summary of key variables to be addressed in the methodology for laboratory studies is presented, to inform future work.

Antifungal Carvacrol Loaded Chitosan Nanoparticles

The increased prevalence and incidence of fungal infections, of which Candida albicans represents one of the most life-threatening organisms, is prompting the scientific community to develop novel antifungal molecules. Many essential oils components are attracting attention for their interesting antifungal activities. Given the chemical and physical characteristics of these compounds, the use of appropriate nanodelivery systems is becoming increasingly widespread. In this study, chitosan nanoparticles were prepared using an ionic gelation procedure and loaded with the phenolic monoterpene carvacrol. After a bioassay guided optimization, the best nanoparticle formulation was structurally characterized by means of different spectroscopic (UV, FTIR and DLS) and microscopy techniques (SEM) and described for their functional features (encapsulation efficiency, loading capacity and release kinetics). The antifungal activity of this formulation was assayed with different Candida spp., both in planktonic and biofilm forms. From these studies, it emerged that the carvacrol loaded nanoparticles were particularly active against planktonic forms and that the antibiofilm activity was highly dependent on the species tested, with the C. tropicalis and C. krusei strains resulting as the most susceptible.

Would carvacrol be a supporting treatment option effective in minimizing the deleterious effects of COVID-19?

The pathophysiological process of the disease, Covid-19, is mediated by innate immunity, with the presence of macrophages responsible for secreting type 1 and 6 interleukins (IL), tumor necrosis factor (TNF) leading to dilation of endothelial cells with a consequent increase in capillary permeability. The treatment of this disease has been much discussed, but the variability in the clinical picture, the difficulties for diagnosis and treatment, especially of those patients who have the most severe clinical condition of the disease. Immunization is an effective tool for controlling the spread and overload of health services, but its effectiveness involves high investments in the acquisition of inputs, development of vaccines, and logistics of storage and distribution. These factors can be obstacles for countries with lower economic, technological, and infrastructure indexes. Reflecting on these difficulties, we raised the possibility of adjuvant therapies with imminent research feasibility, as is the case with the use of carvacrol, a monoterpenic phenol whose has biological properties that serve as a barrier to processes mediated by free radicals, such as irritation and inflammation, due to its antioxidant action. Many authors highlighted the activity of carvacrol as a potent suppressor of COX-2 expression minimizing the acute inflammatory process, decreasing the release of some pro-inflammatory mediators such as IL-1β, TNF-α, PGE2. Anyway, the benefits of carvacrol are numerous and the therapeutic possibilities too. With this description, the question arises: would carvacrol be a supporting treatment option, effective in minimizing the deleterious effects of Covid-19? There is still a lot to discover and research.

Thymus satureioides and Origanum majorana essential oils improve the quality of Beni Arouss buck semen during storage at 4°C

This study aims to investigate the effects of essential oils (EOs), extracted from Thymus satureioides (TS) and Origanum majorana (OM), on Beni Arouss buck semen quality stored in skimmed milk at 4°C. EOs were extracted by hydro-distillation, and the chemical compounds were determined. Ejaculates were collected from six Beni Arouss bucks, once a week for 10 weeks, and they were pooled, divided into five equal aliquots and diluted to 400 × 10⁶ sperm/ml with skimmed milk supplemented with 0.01% of OM EO, 0.01% of TS EO, 0.05% of OM EO and 0.05% of TS EO. Non-supplemented skimmed milk was considered as a control. Semen motility, kinematic parameters, viability, abnormality, membrane integrity and lipid peroxidation were evaluated at 0, 4, 8, 24, 28, 32 and 48 hr of liquid storage at 4°C. The main EO components were carvacrol (31.7%), thymol (28.0%) and borneol (14.4%) for TS, and terpinene-4-ol (31.2%), γ-terpinene (17.4%) and α-terpinene (12.7%) for OM. The results highlighted a dose-dependent effect of TS and OM EOs on all semen quality parameters. 0.01% of both EOs had a beneficial effect on the sperm preservation stored at 4°C compared with control (p < .05) excepted for the straight-line velocity. The 0.05% EO addition had harmful effects during storage particularly for TS EO. In conclusion, 0.01% of TS and OM EOs are recommended to improve the Beni Arouss buck semen preservation at 4°C.

The recent development of thymol derivative as a promising pharmacological scaffold

Thymol (a phenol ring bearing active phytoconstituent) is a privileged scaffold, which is diversified in natural sources. This scaffold acts as an obligatory template for scheming and arriving at designing some newer drug-molecules with potential biological activities. In the pharmacological perspective, the promising active sites of the scaffold are the positions C-1, C-4, and C-6 of thymol that would be accountable for developing potent drug candidates. This review aims to explore the various synthetic routes and the structural-activity relationship of thymol scaffold with suitable active pharmacophore sites.

Chalcones and Bis-Chalcones Analogs as DPPH and ABTS Radical Scavengers

Background:

A number of synthetic scaffolds, along with natural products, have been identified as potent antioxidants. The present study deals with the evaluation of varyingly substituted, medicinally distinct class of compounds “chalcones and bis-chalcones” for their antioxidant potential.

Methods:

In vitro radical scavenging activities were performed on a series of synthetic chalcones 1- 13 and bis-chalcones 14-18.

Results:

All molecules 1-18 revealed a pronounced 2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2ʹ- azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radicals scavenging potential in the ranges of IC50s = 0.58 ± 0.14 - 1.72 ± 0.03 and 0.49 ± 0.3 - 1.48 ± 0.06 μM, respectively. Ascorbic acid (IC50s = 0.5 ± 0.1 and 0.46 ± 0.17 μM for DPPH and ABTS, respectively) was used as a standard radical scavenger.

Conclusion:

Structure-activity relationship (SAR) revealed an active participation of various groups, including -SMe and -OMe in scavenging activity.

Monoterpenes and Their Derivatives-Recent Development in Biological and Medical Applications

Monoterpenes, comprising hydrocarbons, are the largest class of plant secondary metabolites and are commonly found in essential oils. Monoterpenes and their derivatives are key ingredients in the design and production of new biologically active compounds. This review focuses on selected aliphatic, monocyclic, and bicyclic monoterpenes like geraniol, thymol, myrtenal, pinene, camphor, borneol, and their modified structures. The compounds in question play a pivotal role in biological and medical applications. The review also discusses anti-inflammatory, antimicrobial, anticonvulsant, analgesic, antiviral, anticancer, antituberculosis, and antioxidant biological activities exhibited by monoterpenes and their derivatives. Particular attention is paid to the link between biological activity and the effect of structural modification of monoterpenes and monoterpenoids, as well as the introduction of various functionalized moieties into the molecules in question.

Stearic Acid, Beeswax and Carnauba Wax as Green Raw Materials for the Loading of Carvacrol into Nanostructured Lipid Carriers

The use of lipid nanoparticles as drug delivery systems has been growing over recent decades. Their biodegradable and biocompatible profile, capacity to prevent chemical degradation of loaded drugs/actives and controlled release for several administration routes are some of their advantages. Lipid nanoparticles are of particular interest for the loading of lipophilic compounds, as happens with essential oils. Several interesting properties, e.g., anti-microbial, antitumoral and antioxidant activities, are attributed to carvacrol, a monoterpenoid phenol present in the composition of essential oils of several species, including Origanum vulgare, Thymus vulgaris, Nigellasativa and Origanum majorana. As these essential oils have been proposed as the liquid lipid in the composition of nanostructured lipid carriers (NLCs), we aimed at evaluating the influence of carvacrol on the crystallinity profile of solid lipids commonly in use in the production of NLCs. Different ratios of solid lipid (stearic acid, beeswax or carnauba wax) and carvacrol were prepared, which were then subjected to thermal treatment to mimic the production of NLCs. The obtained binary mixtures were then characterized by thermogravimetry (TG), differential scanning calorimetry (DSC), small angle X-ray scattering (SAXS) and polarized light microscopy (PLM). The increased concentration of monoterpenoid in the mixtures resulted in an increase in the mass loss recorded by TG, together with a shift of the melting point recorded by DSC to lower temperatures, and the decrease in the enthalpy in comparison to the bulk solid lipids. The miscibility of carvacrol with the melted solid lipids was also confirmed by DSC in the tested concentration range. The increase in carvacrol content in the mixtures resulted in a decrease in the crystallinity of the solid bulks, as shown by SAXS and PLM. The decrease in the crystallinity of lipid matrices is postulated as an advantage to increase the loading capacity of these carriers. Carvacrol may thus be further exploited as liquid lipid in the composition of green NLCs for a range of pharmaceutical applications.

Chemical Compositions and Anti-Skin-Ageing Activities of Origanum vulgare L. Essential Oil from Tropical and Mediterranean Region

Origanum vulgare L. has been used as a culinary ingredient worldwide. This study revealed the cosmeceutical potential of O. vulgare essential oil as a skin-ageing retardant. The O. vulgare essential oil from a highland area of a tropical country (HO), obtained by hydrodistillation was investigated and compared to a commercial oil from the Mediterranean region (CO). Their chemical compositions were investigated by gas chromatography–mass spectrometry. Antioxidant activities were investigated by ferric reducing antioxidant power, 1,1-diphenyl-2-picrylhydrazyl, and ferric thiocyanate assay. Anti-skin-ageing activities were determined by means of collagenase, elastase, and hyaluronidase inhibition. Carvacrol was the major component in both oils, but a higher amount was detected in HO (79.5%) than CO (64.6%). HO possessed comparable radical scavenging activity to CO (IC₅₀ = 1.8 ± 0.8 mg/mL) but significantly higher lipid peroxidation inhibition (38.0 ± 0.8%). Carvacrol was remarked as the major compound responsible for the reducing power of both oils. Interestingly, HO possessed significant superior anti-skin-ageing activity than ascorbic acid (P < 0.01), with inhibition against collagenase, elastase, and hyaluronidase of 92.0 ± 9.7%, 53.1 ± 13.3%, and 16.7 ± 0.3%, at the concentration of 67, 25, and 4 µg/mL, respectively. Since HO possessed comparable anti-hyaluronidase activity to CO and superior anti-collagenase and anti-elastase (P < 0.01), HO was suggested to be used as a natural skin-ageing retardant in a cosmetic industry.

Heterocyclic β-keto sulfide derivatives of carvacrol: Synthesis and copper (II) ion reducing capacity

Sixteen β-keto sulfide derivatives of carvacrol (4-19) incorporating phenyl or N, O and S heterocyclic moieties were synthesized in three steps. The relationships between heterocyclic structure and cupric, Cu(II), ion reducing antioxidant capacity (CUPRAC) were examined. Nine of the compounds (8-9 and 13-19) showed better CUPRAC activity than trolox at neutral pH, with trolox equivalent antioxidant capacity (TEAC) coefficients ranging between 1.20 and 1.75. Two derivatives (11-12) showed comparable reducing capacity to trolox, with TEAC values of 0.95 for 11 and 1.02 for 12. Compounds 8-9 and 11-19 were more effective at reducing the Cu(II) ion than ascorbic acid and the parent compound, carvacrol. The most effective antioxidants were those containing an oxadiazole, thiadiazole or triazole moiety. In particular, the methyl thiadiazole derivative (15) had the highest Cu(II) ion reducing capacity, with a TEAC coefficient of 1.73.

Carvacrol Loaded Solid Lipid Nanoparticles of Propylene Glycol Monopalmitate and Glyceryl Monostearate: Preparation, Characterization, and Synergistic Antimicrobial Activity

To develop solid lipid nanoparticles (SLNs) with stable lipid matrix structures for the delivery of bioactive compounds, a new class of SLNs was studied using propylene glycol monopalmitate (PGMP) and glyceryl monostearate (GMS) mixtures and carvacrol as a model lipophilic antimicrobial. Stable SLNs were fabricated at PGMP:GMS mass ratios of 2:1 and 1:1, and the carvacrol loading was up to 30% of lipids with >98% encapsulation efficiency and absence of visual instability. Fluorescence spectra and release profiles indicated the carvacrol was successfully encapsulated and homogeneously distributed within the SLNs. SLNs fabricated with equal masses of PGMP and GMS had better stability of carvacrol during storage and higher sphericity than those with a ratio of 2:1 and were much more effective than free carvacrol against Escherichia coli O157:H7 and Staphylococcus aureus. These findings demonstrated the potential applications of the studied SLNs in delivering lipophilic bioactive compounds in food and other products.